The present invention relates to oral compositions containing an anticalculus or an antiplaque/antigingivitis agent.
"Oral composition" means a composition for topical applications to the oral cavity to clean and care for the teeth as well as the oral cavity surfaces. Representatives of such compositions are oral hygiene products and dentifrices such as mouthwashes or rinses, toothpaste, dental gels, tooth powder, chewing gum, lozenges, and similar products. In addition to cleaning teeth to remove dental plaque, the function of oral hygiene preparations is to stop the formation of dental calculus, to prevent dental disorders such as caries, periodontitis and gingivitis, and also to eliminate halitosis.
Dental calculus, or tartar as it is sometimes called, is a hard mineralized material which forms on teeth that consists of inorganic and organic components. The inorganic portion is largely calcium and orthophosphate arranged in a crystal lattice called hydroxyapatite (HAP). The organic portion is derived mainly from microorganisms (i.e., bacteria, yeast, etc.) as well as epithelial cells, white blood cells and food debris.
Formation of dental calculus occurs in two steps. In the first step, plaque is deposited on the teeth. "Plaque" consists of inorganic and organic components derived from saliva, food and bacteria which are present in the oral cavity. Most of the plaque consists of dead and living bacteria surrounded by a gel-like matrix derived from the bacteria and saliva. In the second phase, plaque undergoes calcification to form dental calculus. Initially, amorphous deposits of calcium phosphate begins to appear on and within the matrix of the dental plaque. As the aggregates of calcium phosphate become sufficiently closely packed together, they crystalize to form HAP. The amorphous calcium phosphate, although related to hydroxyapatite, differs from it in crystal structure, particle morphology and stoichiometry.
In addition to being an integral step for the formation of calculus, consequences of the presence of plaque include gingivitis, periodontitis, tooth decay (dental caries) and denture associated problems. Inhibition of oral bacteria involved in the formation of plaque by antimicrobials or antiseptic agents is one means to retard the formation of plaque, thus aiding in preventing or controlling the formation of calculus and other plaque related diseases; see, for example, P. S. Hull, J. Clinical Periodontology, 7, 431-442 (1980). Examples of antiseptic agents include bisbiguanides, such as chlorhexidine and alexidine, and numerous antibacterially active quaternary ammonium compounds, such as cetylpyridinium chloride or the quaternary ammonium compounds described in U.S. Pat. Nos. 3,369,046 and 4,820,507; and quaternary ammonium organosiloxane compounds described in U.S. Pat. No. 4,161,518.
Although the quaternary ammonium compounds are rapidly adsorbed to the tooth surfaces, they exhibit only a moderate degree of efficacy as antiplaque and antigingivitis agents as they are rapidly released from the tooth surface and thus retained in the oral cavity for only a short period of time. Chlorhexidine has been the most successful antiplaque agent as it is believed to bind to the oral mucosa and is thus retained in the oral cavity for a longer period of time than quaternary ammonium compounds. The use of chlorhexidine in oral preparations however, suffers from the following disadvantages: (1) a prolonged bitter after taste lasting up to several hours; (2) after prolonged use stains are produced on the teeth, tongue, gums, oral mucosa and dental restorations; and (3) production of local irritation of the oral mucosa and tongue.
Inhibition of crystalline HAP formation is usually achieved by compounds which sorb onto a growing crystal and disrupt crystal growth. It is well known in the prior art that water soluble hexametaphosphates, tripolyphosphates and pyrophosphates and the like, are effective calcium and magnesium ion sequestrants and/or chelating agents. See, for example, U.S. Pat. No. 3,488,419 which discloses oral compositions containing polyphosphate and U.S. Pat. No. 4,215,105 which discloses oral compositions containing phosphonoacetic acid. However, as described in U.S. Pat. No. 4,627,977, the effectiveness of polyphosphates as anticalculus agents has been limited because they are significantly hydrolyzed by salivary enzymes (phosphatases) to orthophosphates which are ineffective as inhibitors of HAP formation. The amount of enzymatic hydrolysis of the polyphosphate has been reduced by the use of a linear molecularly dehydrated polyphosphate salt combined with fluoride as described in U.S. Pat. No. 4,808,410.
Compounds containing a carbon atom covalently bonded to oxygen, the oxygen being covalently bonded to a phosphorous, herein referred to as C-O-P bonds, particularly six C-O-P bonds, such as phytic acid [myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)], have been recommended for various purposes in oral compositions. U.S. Pat. Nos. 4,259,316 and 4,335,102 disclose oral anticaries compositions containing a phytate compound and a stannous compound. Due to complex formation between polyvalent cations and phytate anion, the art teaches the presence of stannous compounds in an oral composition containing a phytate compound would not be desirable for inhibition of calculus formation.
In U.S. Pat. No. 3,934,002 phytic acid is disclosed as one of the anticalculus compounds in oral compositions used together with a bisbiguanide antiplaque and anticaries agent. These two agents react with one another so that neither the anticalculus or antiplaque agent would be homogeneously distributed throughout the oral compositions. Since both agents are present, if a mouthrinse is prepared, it contains two visibly distinct phases, one being solid phase reaction product of bis-biguanide and anticalculus agent. U.S. Pat. Nos. 4,263,276 and 4,305,928 also describe visually clear oral compositions containing phytic acid in the presence of an alkali metal fluoride, monofluorophosphate or alkali metal monofluorophosphate, where a cationic material, such as a bisbiguanide or cationic surface active agent can be present. However, effective inhibition of HAP or plaque formation with compositions including compounds containing C-O-P bonds with an antimicrobial have not been known beyond such recommendations or speculation.
It would therefore be desirable to have an oral composition containing an effective antiplaque or anticalculus agent to aid in the prevention of dental caries and gingivitis as well as aid in the control of mouth malodor which does not stain the teeth and does not have a bitter taste. It would also be desirable to provide an antiplaque and anticalculus oral composition in which phytic acid is homogeneously distributed in the oral composition along with a cationic antimicrobial compound.
Furthermore, it would be desirable to provide an oral composition having enhanced retention of cationic antimicrobial compounds on the tooth surfaces useful in the prevention of dental plaque and gingivitis.